[JIRA] (IDP-1885) Use constant time algorithm for comparing CSRF tokens

[Philip Smart (Jira)]

Philip Smart ( https://shibboleth.atlassian.net/secure/ViewProfile.jspa?accountId=5afecdc1eb3ffa0c596652c4 ) *created* an issue

Identity Provider ( https://shibboleth.atlassian.net/browse/IDP?atlOrigin=eyJpIjoiN2E1MWM3NTk1MjkwNDFlM2FlOTU4NTM2MGY2MzI0MzYiLCJwIjoiaiJ9 ) / Improvement ( https://shibboleth.atlassian.net/browse/IDP-1885?atlOrigin=eyJpIjoiN2E1MWM3NTk1MjkwNDFlM2FlOTU4NTM2MGY2MzI0MzYiLCJwIjoiaiJ9 ) IDP-1885 ( https://shibboleth.atlassian.net/browse/IDP-1885?atlOrigin=eyJpIjoiN2E1MWM3NTk1MjkwNDFlM2FlOTU4NTM2MGY2MzI0MzYiLCJwIjoiaiJ9 ) Use constant time algorithm for comparing CSRF tokens ( https://shibboleth.atlassian.net/browse/IDP-1885?atlOrigin=eyJpIjoiN2E1MWM3NTk1MjkwNDFlM2FlOTU4NTM2MGY2MzI0MzYiLCJwIjoiaiJ9 )

Issue Type: Improvement Affects Versions: 4.1.4 Assignee: Brent Putman ( https://shibboleth.atlassian.net/secure/ViewProfile.jspa?accountId=557058%3A97de0981-adc3-4044-95ed-131622fad81e ) Components: Security and Cryptography Created: 03/Dec/21 5:39 AM Priority: Trivial Reporter: Philip Smart ( https://shibboleth.atlassian.net/secure/ViewProfile.jspa?accountId=5afecdc1eb3ffa0c596652c4 )

I recently noticed Spring moved (early 20201) their CSRF token matching algorithm from a simple string comparison to one which uses a constant-time algorithm - the help prevent timing attacks.

The IdP uses an injectable validation predicate to compare the tokens, but the default predicate uses a simple string comparison.

We could update the default to a constant-time algorithm. That said, I can not see this is of high importance, my understanding is this becomes an issue if the CSRF token is fixed for a period of time (Spring's default is one token per session) and the attacker attempts different tokens and times how long the response takes: longer times suggest more values are correct in the token. We generate new tokens per view-state, a failed attempt should change the view-state and hence change the token. I will check this, but I guess it would not be hard to change the default if we wanted to.

( https://shibboleth.atlassian.net/browse/IDP-1885#add-comment?atlOrigin=eyJpIjoiN2E1MWM3NTk1MjkwNDFlM2FlOTU4NTM2MGY2MzI0MzYiLCJwIjoiaiJ9 ) Add Comment ( https://shibboleth.atlassian.net/browse/IDP-1885#add-comment?atlOrigin=eyJpIjoiN2E1MWM3NTk1MjkwNDFlM2FlOTU4NTM2MGY2MzI0MzYiLCJwIjoiaiJ9 )

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